Mating for Life? It's Not for the Birds of the Bees

By NATALIE ANGIER

Published: August 21, 1990

AH, romance. Can any sight be as sweet as a pair of mallard ducks gliding gracefully across a pond, male by female, seemingly inseparable? Or better yet, two cygnet swans, which, as biologists have always told us, remain coupled for life, their necks and fates lovingly intertwined.

Coupled for life, with just a bit of adultery, cuckoldry and gang rape on the side.

Alas for sentiment and the greeting card industry, biologists lately have discovered that, in the animal kingdom, there is almost no such thing as monogamy. In a burst of new studies that are destroying many of the most deeply cherished notions about animal mating habits, researchers report that even among species assumed to have faithful tendencies and to need a strong pair bond to rear their young, infidelity is rampant.

Biolgists long believed, for example, that up to 94 percent of bird species were monogamous, with one mother and one father sharing the burden of raising their chicks. Now, using advanced techniques to determine the paternity of offspring, biologists are finding that, on average, 30 percent or more of the baby birds in any nest were sired by someone other than the resident male. Indeed, researchers are having trouble finding bird species that are not prone to such evident philandering.

Faithless Females

''This is an extremely hot topic,'' said Dr. Paul W. Sherman, a biologist at Cornell University in Ithaca, N.Y. ''You can hardly pick up a current issue of an ornithology journal without seeing a report of another supposedly monogamous species that isn't. It's causing a revolution in bird biology.''

In related studies of creatures already known to be polygamous, researchers are finding their subjects to be even more craftily faithless than previously believed. And to the astonishment, perhaps disgruntlement, of many traditional animal behaviorists, much of that debauchery is committed by females.

Tracking rabbits, elk and ground squirrels through the fields, researchers have learned that the females of both species will copulate with numerous males in a single day, each time expelling the bulk of any partner's semen to make room for the next mating. Experts theorize that the female is storing up a variety of semen, perhaps so that different sperm will fertilize different eggs and thus assure genetic diversity in her offspring.

Males Retaliate

Most efficiently energetic of all may be the queen bee, who on her sole outing from her hive mates with as many as 25 accommodating, but doomed drones.

Scientists also have gathered evidence of many remarkable instances of attempts by males to counteract philandering by females. Among Idaho ground squirrels, a male will stick unerringly by a female's side whenever she is fertile, sometimes chasing her down a hole and sitting on top of it to prevent her from cavorting with his competitors. Other squirrels simply use a rodent's version of a chastity belt, topping an ejaculation with a rubber-like emission that acts as a plug.

The new research, say scientists, gives the lie to the old stereotype that only males are promiscuous. ''It's all baloney,'' said Dr. Sherman. ''Both males and females seek extra-pair copulations. And what we've found lately is probably just the tip of the iceberg.'' Even mammals, which have never been paragons of virtue, are proving to be worse than expected, and experts are revising downward the already pathetic figure of 2 percent to 4 percent that represented, they thought, the number of faithful mammal species.

''It was believed that field mice, certain wolf-like animals and a few South American primates, like marmosets and tamarins, were monogamous,'' said Dr. David J. Gubernick, a psychologist at the University of Wisconsin in Madison who studies monogamy in mammals. ''But new data indicate that they, too, engage in extra-pair copulations.''

Scientists say their new insights into mating and the near-universality of infidelity are reshaping their ideas about animal behavior and the dynamics of different animal social systems.

''It's been a bandwagon,'' said Dr. Susan M. Smith, a biologist at Mt. Holyoke College in South Hadley, Mass. ''Nobody can take monogamy for granted anymore, in any species they look at, so we're all trying to rewrite the rules we once thought applied.''

Old Assumptions

Darwin's Misconceptions

Biologists say their new research suggests that many animal social systems might have developed as much to allow animals to selectively cheat as they did out of a need for animals to divide into happy couples. They propose that pair bonds among animals might be mere marriages of convenience, allowing both partners enough stability to raise their young while leaving a bit of slack for the occasional dalliance.

More than anything else, say biologists, they are increasingly impressed by the complexity of animal sexuality. ''It seems that all our old assumptions are incorrect, and that there's a big difference between who's hanging out with whom and who's actually mating with whom,'' said Dr. Patricia Adair Gowaty, a biologist at Clemson University in South Carolina and one of the first to question the existence of fidelity among animals. ''For those of us in the field, this is a tremendously exciting time.''